1. Field of the Invention
The present invention is directed to a pumping system for producing well fluids from petroleum producing formations penetrated by a well. The present invention includes the use of dual parallel tubing strings having the lower portions connected by a crossover flow connection, one of the tubing strings, i.e., the production tubing string, forming a flow path for flowing production fluids to the surface and the other, i.e., the power tubing string, for providing a conduit for inserting, operating and removing a rod-activated pump plunger used to lift well fluids from the well and to move the well fluids up the well to the surface through the crossover flow connection. A flow control valve for controlling production flow is also provided. A lubricating plunger is provided to direct fluid from the annulus between the power tubing and the rods to an area between the barrel of the pump and the lubricating plunger to increase the efficiency of the pump and to assist in sand control.
2. Description of Related Art
Pumping well fluids from wells penetrating producing formations has been done for many years. This is particularly true where heavy viscous oil must be moved to the surface. Often heavy viscous oils such as produced from California formations which are relatively close to the earth's surface contain sand and are difficult to pump. Steam and diluents have often been used to lower the viscosity of heavy crudes to improve flow and pumping efficiency; however, sand is still a major problem.
Heretofore dual tubing strings for a pumping system for producing petroleum have been suggested. For example, pumping installations utilizing parallel dual tubing strings are disclosed in U.S. Pat. No. 4,056,335 to Walter S. Secrest; 3,802,802 to F. Conrad Greer; and 3,167,019 to J. W. Harris.
There is still need, however, for a pumping system having dual production and power tubing strings which permit ease of operation which has movable parts including the pump plunger which may be removed from the power tubing string and replaced in the tubing string without the need for removing the tubing strings from the well, leaving only the pump barrel and tubing in place.